Peptidic transition-state analogs, corresponding to segments in the gpl2O sequence, have been synthesized and used as immunogens for the production of murine monoclonal antibodies. Antibodies harvested from two of these clones produce peptide fragments when incubated with gp120/160, suggestive of proteolytic activity. The putative proteolytic products are being characterized by mass spectrometry. The clones are being grown to produce sufficient amounts of antibody to test for their ability to interfere with the binding of HIV-1 to helper T-cells.